This invention relates to a high-density magnetic drive, and in particular to a highly-reliable magnetic-disk drive having a high track density.
Recently, the capacity of a magnetic-disk drive has increased remarkably; roughly speaking, it has been doubling every three years. This increase in capacity has been attained by improving both the bit density and the track density. However, in order to improve the bit density, it is necessary to narrow the spacing between the head and the medium. In the existing devices, the spacing has been reduced to as small as about 0.2 .mu.m. Thus, it is rather difficult to reduce it by another 0.1 .mu.m or more without deteriorating the slide-withstanding property of the device. In other words, any attempt to further improve the bit density will result in an excessive deterioration in reliability of the device. In view of this, the present invention aims to substantially enlarge the track density of a magnetic-disk drive, thereby making it possible to augment the capacity of the device to a large extent without sacrificing its reliability.
Reducing the track width of a magnetic disk for the purpose of improving its track density will cause the signal to-noise ratio (S/N) thereof to deteriorate. This is particularly true when the head-positioning accuracy is rather poor and reproduction is performed off the track on which the signals to be reproduced are recorded. This not only results in a reduction of signal level corresponding to the deviation from the right track, but allows various background noise attributable to the disordered state of magnetization in those disk areas where no information is recorded to be picked up, which causes a great reduction in the SN ratio, a serious problem in the case where the track width is relatively small. A track width of 5 .mu.m or so may allow a disk device to be realized by some conventional method. However, where the track width is smaller than that, it is necessary to develop a method of improving the SN ratio as much as possible.
A conventional principle in reducing the background noise of a magnetic-disk is described in "Recording Characteristics of Submicron Discrete Magnetic Tracks" (Paper HB-10, Digests of the Intermag Conference, 1987) by S. E. Lambert, I. L. Sanders, A. M. Patlach, and M. T. Krounbi.
Japanese Patent Laid-Open No. 61-24021 discloses a magnetic disk which is capable of performing high-density magnetic recording by virtue of a recess pattern provided between the tracks.